We know that plants don't have a nervous system, but they do respond to light. Light causes chemical changes in many plants causing them to react: opening/closing petals or just following the sun. I also note that if you "wound" many types of trees and shrubs and then bind the wound in moist compost, the plant responds by producing roots.

I'm sure others can find many more examples.

There's a point to all this (Dawkins may already have raised it, I don't know) - the eye is nowhere near as unique as creationists would have people believe.

(There are many types of eye that have evolved over the years in the animal and insect kingdoms but this isn't the point here).

Although our eyes are the product of millions of years of evolution, the actual process that works them (chemical changes in cells due to the interaction with light) has not altered that much. My understanding is that persistence of vision (the wonderful effect that allows us to enjoy movies) is largely due to the "slow" reactions of the chemistry involved.

Now, if we know that vision is the result of a chemical reaction and that a plant also responds to a light using a photo-reactive chemical change, it's not a huge jump to note the fundamental connection and another demonstration that evolution created us.

Replies to This Discussion

That's a good point, but wouldn't it be more convincing to observe that virtually every organism on the planet has DNA? And not only that, but we share a large % genes with all other animals AS WELL AS PLANTS. This is much more compelling than narrowing the arguement to photoreceptivty.

While I'd agree that you can only "Lead a horse to water..." the difficulty with DNA is that you can't see it.

This example is only another example to add to our armory! ;-)

The big problem we're facing is that the idiots are out-breeding us. There was a time, some millenia ago, that we had larger brains and our ancestors evolved smaller brains to survive. Current "evolution" is driven by idealistic altruism but it does not favor the intelligent; it favors the drop-out dads and mothers who have multiple partners... It favors the Roman Catholic idea of huge families.

We're part of a huge course correction - and the likes of you and I are going to go extinct.

I think otherwise - the Roman Catholic Church has accepted evolution (even though with a caveat), the general population is becoming more non-religious, if not atheist, and young fundies are dropping some of their rigid beliefs and taking up some "liberal" activities.

We live in a technological society and fewer and fewer people know how to maintain let alone create it.

Worse, all the climate change deniers (etc.) are having more children than the more careful "educated" people because they see things differently - they don't plan ahead; we do and it will be our undoing.

I've put some thought into this, with regard to science fiction. I always hate when science fiction lazily uses earth classifications for their organisms. I get it, your imagination is limited, but you could, at least not call it Bajoran wheat. Wheat refers to a group of organisms that are all related and share an evolutionary history. Even if you had something that looked exactly like wheat, it wouldn't actually BE wheat.

Organs are different in this respect because what we call an eye has evolved multiple times throughout evolutionary history. An organ can be defined by its function. Therefore, I wouldn't begrudge calling any organ with a lens that focused light and sent that information to the brain, an eye.

But ah, I don't guess these are really eyes, exactly, but they're definitely photosensitive, and utilize proteins that are photosensitive, and the earliest eye-like organs did that, but without a lens, I dunno if I'd call it an eye, exactly.

Completely with you on that - I'm just looking for novel explanations to throw the usual suspects off track. Unless they're connected to the Internet and have a ready explanation, this sort of stuff really plays hell with them.

I'm growing a couple of Triops right now - they have three eyes although I'm unsure if the nauplus eye actually has a lens at all.I'm not all that keen on Wikipedia, but this picture should be OK...

I'd agree that this behavior is more akin to stem cells than even a primitive organelle, but it goes some way to show how a simple eye can come about and anything that flummoxes a cretinist has to be a good thing! ;-)

At what point does a cluster of light sensitive photo-receptors become functional optical eyes? Specialized cells that detect and react to light is, in my view, the base requirement for an eye, then light / dark differentiation and movement and the neural equipment capable of processing and reacting. True, a plant has a photo reaction (a tropism ) but the mechanism does not resemble animal eyesight. We can determine up and down by the pressure on our feet, strain on certain muscles and the little leveling doodad in our inner ear. Plants can also determine up and down but, again, not with the same mechanisms also true of water sensing Hydro -tropism, or touch Thigmo-thropism, Thermo-tropism, Chemo-tropism and a few more. All of the tropisms are survival positive attributes. Having said all of that I am convinced that we know very little of plant awareness states of its environment - if any exist. Studies to answer that question are not what could be called robust. However, in a world falling off the edge of starvation - the more we know about the plants that feed us is a worthy goal.